Monolithic optical emitter-detector

ABSTRACT

Optical feedback control in an optical emitter-detector combination can be improved by fabricating the two devices on a single substrate. The feedback radiation can then travel within a monolithic structure. This arrangement will yield greater uniformity in devices as well as provide for easier mechanical assembly.

This is a continuation-in-part, of application Ser. No. 08/129,814 filedSep. 30, 1993, now abandoned.

FIELD OF THE INVENTION

This invention generally relates to optical electrical components.Specifically, the invention is directed to monolithic emitter-detectordevices.

The invention is related to the bidirectional coupler of the typedescribed in copending U.S. Patent Application entitled "LinearBidirectional Optocoupler" by Robert Krause, the applicant herein, filedon Sep. 30, 1993 as U.S. patent application Ser. No. 08/129,640. Theforegoing application is assigned to the same assignee as the presentpatent application and the details of it are incorporated herein byreference.

BACKGROUND OF THE INVENTION

Typically, optical emitters with a provision for optical output (poweror flux) control using optical feedback are configured as a discreteemitter and a discrete optical detector. Such devices can be used assources in linear optical couplers, as accurately controlled opticalsources for meteorology applications, and in medical and industrialapplications for absorption and reflection measurements.

In fabricating such devices, the emitter and detector are commonlyplaced on separate substrates because of the dissimilarity in materialsand manufacturing processes--most detectors are fabricated from siliconwhile the emitters are gallium arsenide (GaAs) based. To obtain opticalfeedback, the radiation from the emitter is optically coupled back tothe detector through an optical cavity.

By having the emitter and detector as discrete components, the cost ofmanufacturing the devices remains high. Two substrates are required inaddition to the connections between the devices and outside circuitry.It is therefore desirable to provide an alternative device that offerslower fabrication costs.

SUMMARY OF THE INVENTION

The aforementioned problems are obviated by the present invention thatprovides a single monolithic emitter-detector. Although monolithic diodearrays are common, an example being a seven-segment configuration fordigital readout applications, such arrays share a common substrate andare designed to have minimal crosstalk or optical coupling between diodeelements. However, such coupling or crosstalk is desirable between theemitter and detector here, since it enhances the feedback from theemitter to the detector.

One embodiment of the invention is an emitter and a detector opticallycoupled within a monolithic substrate. The emitter could be fabricatedfrom groups III-V or II-VI material and the detector from PN or PINmaterials.

Possible configurations for the monolithic emitter-detector include aside-by-side layout where the emitter and detector are coupled at oneedge, a peripherally-coupled device, and a vertically-configuredarrangement with edge coupling. These are but three examples; otherconfigurations are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, as well as otherobjects and advantages thereof not enumerated herein, will becomeapparent upon consideration of the following detailed description andthe accompanying drawings, wherein:

FIG. 1 is a top-view of a monolithic optical emitter-detector of thepresent invention where the emitter and detector are edge-coupled;

FIGS. 2-5 are cross-sectional views of monolithic opticalemitter-detectors of the present invention where the emitter anddetector are peripherally-coupled;

FIGS. 6-8 are cross-sectional elevation views of monolithic opticalemitter-detectors of the present invention where the emitter anddetector are vertically-coupled;

FIGS. 9-16 are schematic diagrams of monolithic opticalemitter-detectors of the present invention where the emitter detectorare vertically-coupled; and

FIG. 17 is a block diagram of an application of the monolithic opticalemitter-detector of the present invention.

FIG. 18 is a top view of the monolithic optical emitter-detector of FIG.1 where the detector has a shield layer;

FIG. 19 is a cross-sectional elevation view of a monolithic opticalemitter-detector of FIG. 1 where the detector has a shield layer;

FIG. 20 is a cross-sectional elevation view of the monolithic opticalemitter-detector of FIG. 6 where the detector has a shield layer;

FIG. 21 is a cross-sectional elevation view of the monolithic opticalemitter-detector of FIG. 7 where the detector has a shield layer; and

FIG. 22 is another cross-sectional elevation view of the monolithicoptical emitter-detector of FIG. 8.

DETAILED DESCRIPTION

The devices described here are based in part on the technology used inthe Siemens® IL300 family of aluminum gallium arsenide (AlGaAs) linearoptocouplers, discussed in the Siemens Optoelectronics Data Book 1993,pp. 5-115 through 5-122, and pp. 11-177 through 11-193. It should beunderstood that other devices can be used. Also, the couplers could beused with other types of electromagnetic radiation, such as infraredradiation or ultraviolet light.

One configuration of a monolithic emitter-detector constructed inaccordance with the present invention is shown in FIG. 1. Theemitter-detector assembly 10 has a two diodes, an emitter D1 12 and adetector D2 14 on a single substrate 16. The emitter 12 and the detector14 are adjacent or side-by-side, providing edge coupling through thesubstrate 16 in the region 18 shared by the two components 12 and 14.

In making the device 10, the LED wafer is sliced in such a fashion thattwo diodes remain attached to one another at one edge. Insulationbetween the adjacent diodes can be achieved by using either mechanicalor chemical deposition methods. The device can be packaged as athree-lead LED or perform as a servo-controlled emitter in a linearcoupler.

Monolithic emitter-detector devices can also be configured such that theemitter and detector are connected by a lateral, peripheral edge, asillustrated in FIGS. 2 through 5. In FIG. 2, the monolithicemitter-detector 30 shown has an emitter D1 32 that is physicallysurrounded by a detector D2 34. The emitter 32 and the detector 34 arepositioned on a substrate 36. Coupling occurs at a peripheral edge 38.The emitter 32 can have any suitable shape such as round, oval, square,rectangular, curvilinear, or interdigitated.

A similar monolithic emitter-detector 50 is shown in FIG. 3. Here, theemitter D1 52 surrounds the detector D2 54. Coupling occurs as in thedevice of FIG. 2 at a peripheral edge 58.

For illustration purposes, monolithic emitter-detectors 70 and 90 havinground or oval emitters and detectors are shown in FIGS. 4 and 5,respectively. Each has its respective emitter D1 72 or 92 and detectorD2 74 or 94.

The devices of FIGS. 2-5 can be packaged as a three-lead LED or performas a servo-controlled emitter in a linear coupler.

Monolithic emitter-detectors having vertically-coupled surfaces areshown in FIGS. 6-8. The first such device 110, in FIG. 6, has asubstrate 112, an emitter 114, and a detector 116. The detector 116 canbe physically or chemically grown on top of the emitter 114, the twobeing insulated from one another. The emitter 114 radiates through thedetector 116 or through the substrate 112 if it is sufficientlytransparent.

A second device 130 is shown in FIG. 7. Similar to the device in FIG. 6,this device 130 has a substrate 132, an emitter 134, and a detector 136.A window 138 in the detector 136 is provided by physical or chemical(etching) means and allows the optical radiation from the emitter 134 topass through.

Finally, a third device 150 is depicted in FIG. 8. The device 150 has asubstrate 152, a detector 154, and an emitter 156. The emitter 156radiates upwardly, but some of its radiation also passes through thesurface adjacent the detector 154, providing feedback to the detector154 and permitting maximum coupling out of the emitter's 156 majorradiating surface 158. Another rendering of the device 150 of FIG. 8 isshown in the cross-sectional elevation view of FIG. 22. This figurefurther illustrates that the detector 154 is shielded by the emitter156.

In addition to positioning the detector over the emitter, or thereverse, the orientation of the anodes and cathodes of each diode mustbe considered. In FIGS. 9 through 16, eight variations are illustrated.In the devices shown in FIGS. 9 through 12, detectors 170 are positionedabove emitters 172, which in turn sit on substrates 174. In the devicesshown in FIGS. 13 through 16, the detectors 170 sit directly on thesubstrates 174, and the emitters 172 are positioned above the detectors170.

Returning to FIGS. 9-12, the four circuits differ in how the diodes areinterconnected. In the first (FIG. 9), the cathode 176 of the detector170 is connected to the anode 178 of the emitter 172, while the anode ofthe detector 170 of the second device (FIG. 10) is connected to thecathode of the emitter 172. For the third and fourth devices, either theanodes (FIG. 11) or the cathodes (FIG. 12) are connected to each other.In the case of the emitter/detector/substrate arrangement of FIGS.13-16, similar variations of diode interconnections are illustrated.

An application of the monolithic optical emitter-detector of the presentinvention is shown in FIG. 17. The circuit shown is a linear coupler ofthe kind discussed in the copending application referenced above. Thecoupler has an input 200 that drives a control amplifier 202. Theamplifier 202 has a signal input 204, a feedback input 206, and anoutput 208. The signal input 204 of the amplifier 202 is connected tothe coupler input 200.

The next stage of the coupler is a monolithic emitter-detector 210,which has an emitter 212, a detector 214, and a substrate 216. Theoutput 208 of the control amplifier 202 is provided to the emitter 212;the detector 214 provides a feedback signal 218 to the feedback input206 of the amplifier 202. Optical radiation 222 generated by the emitter212 illuminates an output detector 222 that generates an output 224,providing isolation between the input 200 and the output 224. At thesame time, the detector 214 is receiving optical radiation 226 from theemitter 212 to develop the feedback signal 218.

Virtually the same circuitry can be used to construct aconstant-controllable output flux LED lamp. Instead of an outputdetector 222, the optical radiation 220 of the emitter 212 is receivedby a human or electronic receiver 230 as appropriate to the application.

The detector in each of the configurations responds only to energy fromthe emitter received through the substrate or directly from an adjacentsurface. The detector may be shielded from extraneous sources of energyby an opaque layer or by virtue of being packaged in an enclosureimpervious to light. For example, as shown in FIGS. 18 and 19, detectorD2 14 has a shield layer 250. The only energy reaching detector D2 14originates at the emitter D1 12 and travels through the substrate 16.Similarly, in the configurations of FIGS. 6 and 7, shields 260 and 270are provided as shown in FIGS. 20 and 21, respectively. Additionally,optional reflectors 280 are provided for the configurations of FIGS. 20and 21 to provide an additional path for the optical energy generated bythe emitter. The reflectors 280 could be situated outside of thesubstrate (112 or 132) if preferred.

While there has been described what is believed to be the preferredembodiment of the invention, those skilled in the art will recognizethat other and further modifications may be made thereto withoutdeparting from the spirit of the invention, and it is intended to claimall such embodiments that fall within the true scope of the invention.For example, other configurations and geometries of the emitter anddetector are contemplated.

What is claimed is:
 1. A monolithic apparatus, comprising:means foremitting radiation positioned on the means for supporting; and means fordetecting radiation positioned on the means for supporting adjacent tothe means for emitting, wherein the means for emitting is electricallycoupled to the means for detecting and the means for detecting receivesradiation only from the means for emitting.
 2. The apparatus as setforth in claim 1, wherein the means for supporting is a non-insulatingsemiconductor substrate.
 3. The apparatus as set forth in claim 1,wherein the means for emitting is electrically coupled to the means fordetecting through the means for supporting.
 4. The apparatus as setforth in claim 1, wherein the means for emitting and the means fordetecting are coplanar.
 5. The apparatus as set forth in claim 1,wherein the means for emitting and the means for detecting arephysically joined at at least one point.
 6. The apparatus as set forthin claim 1, wherein the means for detecting surrounds the periphery ofthe means for emitting.
 7. The apparatus as set forth in claim 1,wherein the means for emitting surrounds the periphery of the means fordetecting.
 8. The apparatus as set forth in claim 1, wherein the meansfor emitting and the means for detecting have generally roundgeometries.
 9. The apparatus as set forth in claim 1, wherein the meansfor emitting and the means for detecting have generally oval geometries.10. The apparatus as set forth in claim 1, wherein the means foremitting and the means for detecting have generally curvilineargeometries.
 11. The apparatus as set forth in claim 1, wherein the meansfor emitting and the means for detecting have generally rectangulargeometries.
 12. The apparatus as set forth in claim 1, wherein the meansfor emitting and the means for detecting have generally squaregeometries.
 13. The apparatus as set forth in claim 1, wherein the meansfor emitting generates visible radiation.
 14. The apparatus as set forthin claim 1, wherein the means for emitting generates infrared radiation.15. The apparatus as set forth in claim 1, further including means forallowing radiation to pass out of the apparatus.
 16. The apparatus asset forth in claim 1, further including means for shielding the meansfor detecting radiation.
 17. A monolithic apparatus, comprising:meansfor supporting; means for emitting radiation positioned on the means forsupporting; and means for detecting radiation positioned on the meansfor emitting, wherein the means for emitting is electrically coupled tothe means for detecting and the means for detecting receives radiationonly from the means for emitting.
 18. The apparatus as set forth inclaim 15, wherein the means for detecting comprises means for allowingradiation to pass out of the apparatus.
 19. The apparatus as set forthin claim 18, wherein the means for allowing radiation to pass out of theapparatus is an etched window.
 20. The apparatus as set forth in claim17, wherein the means for supporting is a non-insulating semiconductorsubstrate.
 21. The apparatus as set forth in claim 17, wherein the meansfor detecting is a diode having a cathode and the means for emitting isa diode having an anode, and the cathode is coupled to the anode. 22.The apparatus as set forth in claim 17, wherein the means for detectingis a diode having an anode and the means for emitting is a diode havinga cathode, and the anode is coupled to the cathode.
 23. The apparatus asset forth in claim 17, wherein the means for detecting and the means foremitting are diodes, each diode having an anode, and the anodes arecoupled to one another.
 24. The apparatus as set forth in claim 17,wherein the means for detecting and the means for emitting are diodes,each diode having a cathode, and the cathodes are coupled to oneanother.
 25. The apparatus as set forth in claim 17, wherein the meansfor emitting generates visible radiation.
 26. The apparatus as set forthin claim 17, wherein the means for emitting generates infraredradiation.
 27. The apparatus as set forth in claim 17, wherein the meansfor emitting radiates through the means for detecting.
 28. The apparatusas set forth in claim 17, further including means for shielding themeans for detecting radiation.
 29. A monolithic apparatus,comprising:means for supporting; means for detecting radiationpositioned on the means for supporting; and means for emitting radiationpositioned on the means for detecting, wherein the means for emitting iselectrically coupled to the means for detecting and the means fordetecting receives radiation only from the means for emitting.
 30. Theapparatus as set forth in claim 29, wherein the means for detecting is adiode having a cathode and the means for emitting is a diode having ananode, and the cathode is coupled to the anode.
 31. The apparatus as setforth in claim 29, wherein the means for detecting is a diode having ananode and the means for emitting a diode having a cathode, and the anodeis coupled to the cathode.
 32. The apparatus as set forth in claim 29,wherein the means for detecting and the means for emitting are diodes,each diode having an anode, and the anodes are coupled to one another.33. The apparatus as set forth in claim 29, wherein the means fordetecting and the means for emitting are diodes, each diode having acathode, and the cathodes are coupled to one another.
 34. The apparatusas set forth in claim 29, wherein the means for emitting generatesvisible radiation.
 35. The apparatus as set forth in claim 29, whereinthe means for emitting generates infrared radiation.
 36. The apparatusas set forth in claim 29, wherein the means for supporting is anon-insulating semiconductor substrate.
 37. The apparatus as set forthin claim 29, further including means for allowing radiation to pass outof the apparatus.
 38. The apparatus as set forth in claim 29, furtherincluding means for shielding the means for detecting radiation.
 39. Themonolithic optical emitter-detector as set forth in claim 38, furtherincluding an opaque shield layer or an enclosure impervious to light.40. The monolithic optical emitter-detector as set forth in claim 38,further including an opaque shield layer or an enclosure impervious tolight.
 41. The monolithic optical emitter-detector as set forth in claim38, further including an opaque shield layer or an enclosure imperviousto light.
 42. A monolithic optical emitter-detector, comprising:asubstrate; an emitter positioned on the substrate; and a detectorpositioned on the substrate adjacent to the emitter, where the detectoris electrically coupled to the emitter and receives radiation only fromthe emitter.
 43. A monolithic optical emitter-detector, comprising:asubstrate; an LED emitter positioned on the substrate; and a detectorpositioned on the emitter, where the detector is electrically coupled tothe emitter and receives radiation only from the emitter.
 44. Amonolithic optical emitter-detector, comprising:a substrate; a detectorpositioned on the substrate; and an LED emitter positioned on thedetector, where the detector is electrically coupled to the emitter andreceives radiation only from the emitter.